The present invention relates to a display unit by cathodoluminescence excited by field emission. It more particularly applies to the production of simple displays, permitting the display of fixed images or pictures, and to the production of complex multiplexed screens, making it possible to display moving pictures, such as television pictures.
Cathodoluminescence display units are already known, which use a thermoelectronic emission. A particular construction of such units is diagrammatically represented in FIG. 1 and comprises a plurality of anodes coated with a cathodoluminescent substance or phosphor 2 and arranged in parallel lines on an insulating support 4, together with a plurality of filaments 6 able to emit electrons when heated and which act as cathodes, said filaments being arranged along lines parallel to the anodes. A plurality of grids 8 are placed between the anodes and the filaments, being arranged in parallel columns and the latter are perpendicular to the lines or rows. The assembly constituted by the anodes, the filaments and the grids are exposed or bared in a transparent box or casing 10, which is sealingly connected to support 4. When heated, the filaments 6 emit electrons and an appropriate polarization of a filament, grid and anode enable the electrons emitted by said filament to strike the anode, which is then subject to light emission. By matrix addressing of the rows of anodes and columns of grids, it is in this way possible to produce images or pictures, which are visible through the transparent casing 10.
Such display units suffer from the disadvantages of the definition of the images which they make it possible to obtain not being of a high quality, the devices or units are complicated to produce and they have a high electric power consumption, in view of the fact that the filaments have to be heated.
The principle of electronic emission by field effect is also known, which is also called "field emission" or "cold emission". This principle has already been used for applications unlinked with visual display. It is diagrammatically illustrated in FIG. 2 where, in a vacuum, metal points 12 serving as cathodes and placed on a support 14, are able to emit electrons when an appropriate voltage is established between them and an anode 6 positioned facing said points.